Earth sciences

Species richness and population limitation in insect parasitoid-host systems

Article Abstract:

The degree at which parasitoids limit insect population is positively correlated to the species richness of the parasitoids. This relationship is tested using data on parasitoids attacking herbivorous insects and worldwide biological insect control. Parasitoid infestation of insects is affected by refuges insects seek to escape harm. These refuges are provided by plants and soil or may result from the insect's mobility. Refuges protect the insect and decrease parasitoid diversity. Thus, the key to effective biological insect control may depend on the ability of parasitoids to seek and consequently parasitize insect hosts.

Accumulation of native parasitoid species on introduced herbivores: a comparison of hosts as natives and hosts as invaders

Article Abstract:

Parasitoid attacks on species of herbivores were lower when parasites were introduced to hosts as invaders rather than as natives. The overall parasitoid richness shows a weak tendency to increase with duration in the region of introduction over the first 150 years. The biological characteristics of herbivores, and intrinsic and extrinsic region-specific factors, might play important roles in setting parasitoid richness levels on hosts as natives and on hosts as invaders. The structure of 87 parasitoid complexes is compared with those on the same herbivore species in their native regions.

Parasitoid species richness, host mortality, and biological control

Article Abstract:

The relationships among parasitoid species richness, host mortality from parasitoids and the effects of parasitoids on host populations were investigated. The study protocol involved obtaining larval and pupal primary parasitoids known from more than 2,000 holometabolous insect species in 110 families from 86 countries. The results showed that parasitoid species richness is related to parasitoid effects on host populations, particularly the susceptibility of hosts to parasitoid. The effect of the presence of host refuges to parasitoid-host interactions are also discussed.